As environmental consciousness has been enhanced in recent years, demands are increasing for solventless painting techniques and alternatives to plating effective for decoration of molded articles such as building materials, automobile parts, portable telephones, home electric appliances, and personal computers. In particular, the use of film in decoration methods has been widely practiced.
Against such a background, the use of biaxially stretched polyester film as a molding film designed to be processed by printing and molding has been proposed (see Japanese Unexamined Patent Publication (Kokai) No. 2001-347565). There are also proposals to use polyester, copolymerized polyester resin in particular, as a deep-draw moldable sheet that can be molded and decorated simultaneously since polyester is more suitable for low stress molding than polyethylene terephthalate (hereinafter occasionally referred to as PET) (see Japanese Unexamined Patent Publication (Kokai) No. 2000-238070). There are also proposals of film formed by attaching polyolefin film at least to one side of unstretched polyester film and designed for use as printable and coatable film material for transfer foil production (see Japanese Unexamined Patent Publication (Kokai) No. 2004-188708). In addition, special films such as mold releasing film and decorative film that are based on cyclic polyolefin resin have also been proposed (see Japanese Unexamined Patent Publication (Kokai) Nos. 2006-257399 and 2005-162965).
In addition to moldability, molding film is also required to have other characteristics. For example, film for transfer foil should have good appearance features including smoothness and glossiness on the transfer surface for coating with a decorating layer as a base film. In general, however, windability of a film during production and processing steps deteriorates if an attempt is made to produce a film with a smooth surface. Importance is attached to the smoothness of film surfaces in the field of optical applications as well as in the field of moldings, and some film production methods that can solve the above problem in the former field have been proposed including optical films processed by the so-called knurling technique (also referred as rouletting and embossing) that have a roughened part along the film edges to improve windability (see Japanese Unexamined Patent Publication (Kokai) No. 2011-224934).
The film described in JP '565, which is a biaxially oriented polyester film, is not sufficiently high in moldability at low temperatures, though high in heat resistance.
The film described in JP '070 is too low in solvent resistance to resist printing and coating.
The film described in JP '708 is based on polypropylene as the polyolefin component and, accordingly, is poor in appearance quality and cannot be applied to products that require a high degree of surface properties.
The films described in JP '399 and JP '965 are not designed with great care in terms of appearance quality and film processability.
Except for the film edge parts with a roughened surface part, the film described in JP '934 is not designed with great care in terms of windability of non-knurled parts in film production and processing steps.
It could therefore be helpful to provide molding film high in both windability during film production and processing steps and transfer surface smoothness and also excellent in appearance quality and moldability.